Fifty years ago — the men dressed in suits and ties, the women in knee-length skirts — 3,000 students flooded auditoriums on the University of Michigan campus.

A group of faculty members had decided to organize a work stoppage against the Vietnam War.

Instead, on March 24, 1965, the gathering became the first teach-in — a 12-hour marathon of lectures, Q&A's, movies and workshops — which still serves today as a blueprint for college campus protests across the country.

Fueled by free coffee, they endured bomb threats as they learned about what was going on in Vietnam, a small country along the South China Sea few Americans could find on a map.

The war pitted the American-backed South Vietnam against the Communist North Vietnamese; Washington viewed it as necessary to contain the spread of its Cold War enemy's influence.

An Ann Arbor draft board sit-in had an impact, in this undated photo.(Photo: AP)

Fifty years later, those in the middle of it recall that historic night and its impact.

"There was a lot of urgency, excitement, gladness that people were awake and engaged. There were a lot of people talking to one another," said Alan Haber, a co-founder of the student activist group Students for a Democratic Society, which held its first meeting at the U-M campus in 1960. "It was buzz, buzz, buzz all the time. People forget now the urgency, the desperation of the time."

The university is commemorating that first teach-in with a program this Friday and Saturday called "Teach-In +50: End the War Against the Planet." This event will focus on climate change and possible solutions, but will feature many veterans of the original 1965 teach-in.

The teach-in was originally conceived in February 1965 as a work moratorium, recalled one of the organizers, William Gamson, then a 31-year-old U-M associate professor of sociology.

Gamson has the letter he wrote to the school asking that they dock his pay for that day of missed work. But while he had tenure, other faculty organizers of the work stoppage didn't. They decided at the last moment to change the event into an all-night teach-in.

The scheduled speakers were Gamson; Robert Browne, formerly of Aid for International Development and a six-year resident of Vietnam; John Donahue of Michigan State University's anthropology department, and a field worker in Vietnam, and Arthur Waskow, then a resident fellow at the Institute for Policy Studies in Washington, and today a rabbi.

"I remember at 3 a.m. looking a little groggily at the clock. I thought, 'I've taught many seminars at 3 p.m. in the afternoon, but I've never taught a 3 a.m. seminar before,'" recalled Waskow. "It was very powerful, because it was so strange. I think it was brilliant."

Next came a torch-lit protest on the library stairs from midnight to 1:30 a.m. with Frithjof Bergmann of the philosophy department, Kenneth Boulding of the economics department, Haber, and campus minister J. Edgar Edwards.

After that was two rounds of seminars — eight held simultaneously — from 1:30-3 a.m. and 4-6 a.m., along with continuous movie screenings, a protest workshop and a meeting to plan further actions.

The concluding rally, 7-8 a.m. on the library steps, featured Thomas Mayer of the sociology department and Nancy Gendell of Ann Arbor Women for Peace.

Haber, Gamson and Waskow said they think most of the people who came to the teach-in knew little about Vietnam and wanted to learn more about what was going on halfway around the world.

Gamson recalled some singing during the 12-hour event and the attendees bringing food to sustain them, along with the free coffee, during the long night. He distinctly remembers how well the participants were dressed.

"There was an effort to present ourselves as 'We're not extremists, we're not crazies. We're regular mainstream people that are against the war and we're not a marginal fringe group,' " he said. "There was effort to look respectful."

Even when a police officer handed him a note saying there was a bomb threat and everyone needed to evacuate Angell Hall, the participants acted in a dignified way. Gamson, today a sociology professor at Boston College, kept that piece of paper, too.

During the evacuation, participants were turned out into the snowy cold and faced taunts from pro-war protesters. "Nuke Hanoi" read one sign.

"There was name-calling and nothing physical," recalls Gamson. "They were calling us communists or commie sympathizers and we were probably calling them fascists or McCarthyites."

Haber, whose father was then the dean of Literature, Science and the Arts, plans to attend this week's commemoration, as do many who were in the same auditorium half a century earlier.

"It was a crucial step in the formation of the antiwar movement in the United States," said Waskow. "It was not just a small group of a couple thousand students, marching in Washington. Also, it taught people in 1965 who knew diddly squat about Vietnam ... There was really learning that happened."

Said Gamson, "A lot of people talked about it as the most meaningful experience they'd had at the University of Michigan. It had dramatic effect on people and lot of people remember it vividly." He said people often come up to him to say they were there that night.

But change did not come, overnight. The U.S. would continue to fight in Vietnam until 1975. "The struggle went on for a much longer time than we'd hoped," Gamson reflected.